For many purposes it is desirable to apply a surface layer of a foil or other material in the form of a web to a plate-shaped substrate or board, for protective, decorative or like reasons.
For example, in the production of pressed board, a decorative, color-imparting, design or other esthetically pleasing layer may be applied to the pressed board substrate for use in construction, furniture or the like. A foil of thermally bondable material, which is free from a pattern and may be transparent, can be provided to protect the surface of a pressed-board or plywood or other laminated substrate to protect the surface of the substrate or a decorative coating or foil which has previously been bonded thereto or to make the resulting board impervious to liquids.
Furthermore, a foil of thermally bondable material or other web-like material can also be applied to boards and like substrates for a variety of other reasons, e.g. to create patterned textures or patterns thereon.
In all such cases, apparatus for the application of the foil web for the thermal bonding of the foil web to a substrate may be desired.
It has already been proposed to apply foil webs to such substrates using apparatus in which the substrate is displaced past the laminating head or unit on a belt conveyor, the latter unit being provided with means for drawing the foil web from a supply roll and pressing the web against the substrate carried past the stationary head by the conveyor. The conveyor can be continuously or intermittently (cyclically) driven and either the substrate or the foil can, when thermally fusible materials are not involved, be provided with coatings of an adhesive which is thermally activatable, either for softening of the adhesive so as to effect the bonding or to polymerize or otherwise harden or set the adhesive.
The system is thus capable of a number of modes of thermal lamination, by which term I understand to include all continuous or intermittent processes for applying foils of various kinds to plate-shaped workpieces. However, this description should be understood as being especially applicable to the coating of particle board, fiber board and the like with finishing foils and decorative foils having a finished upper surface which will constitute an outer surface of the board. In this case the particle or chip board, fiber board or the like will constitute the substrate. While the particle or fiber board may be composed of wood particles or fibers or even more generally, of cellulose fiber, sawdust and the like, materials other than wood substrates or nonwood substrates can be used.
The foils with which the present disclosure is concerned are primarily resin-impregnated papers, carrier-free synthetic-resin foils and so-called thin foils of partially impregnated or coated paper. The foils can also be paper webs, generally previously coated with a synthetic-resin film or printed with a decorative pattern.
Coating units of the aforedescribed type are described in Verbund von Holzwerkstoff und Kuststoff in the Mobelindustrie,VDE-Verlag GmbH, pp. 93-107. All of the foils there described and all of the substrates mentioned can be used for the purposes of the present system as well.
In this publication, the laminating apparatus comprises a plurality of calendering-roll pairs which perform various functions. For example, one pair of rolls can be used to bond the substrate to the foil, another pair of rolls can be used for embossing and yet a third pair of rolls for smoothing the laminated body. Calender rolls of this type must be synchronized with relatively complex control devices and technology and the problem of synchronization is even more pronounced when the laminating is to be carried intermittently or periodically, i.e. when spaced apart substrates are to be passed through the system and intervals are provided between laminating operations. Furthermore, with such systems serious difficulties have been encountered with respect to the quality of the product when the lamination is to be carried out at relatively high speed. The quality defects are first and foremost manifested in deterioration of the surface quality of the product.